Narcotine, another of the opium alkaloids, when heated with manganese dioxide and sulphuric acid, is oxidized and splits apart into opianic acid, C_{10}H_{10}O_{5}, and cotarnine, C_{12}H_{13}NO_{3}.  This latter, by careful oxidation, yields apophyllenic acid, C_{8}H_{7}NO_{4}, and this, on heating with hydrochloric acid to 240 deg.  C., yields pyridine-dicarboxylic acid, C_{5}H_{9}N(COOH)_{2}.  The base cotarnine also results from the prolonged heating of narcotine with water alone.  In this case, instead of opianic acid, its reduction product meconine, C_{10}H_{10}O_{4}, is produced.

Meconic acid, C_{7}H_{4}O_{7}, which is found in opium in combination with the different bases, has also been investigated.  By acting upon meconic acid with ammonia, comenamic acid is formed, and this latter, when heated with zinc dust, yields pyridine.

If we go now to the cinchona alkaloids, we meet with exceedingly interesting results. Quinine, C_{20}H_{24}N_{2}O_{2}, when carefully oxidized with chromic acid or potassium permanganate, yields a series of products.  First is formed quitenine, C_{19}H_{22}N_{2}O_{4}, a weak base, then quininic acid, C_{11}H_{9}NO_{3}, then the so-called oxycinchomeronic acid, C_{8}H_{5}N0_{6}, and finally cinchomeronic acid, C_{7}H_{6}NO_{4}.  Now the two acids last mentioned are simple substitution products of pyridine, oxycinchomeronic acid being a pyridine-dicarboxylic acid, C_{5}H_{2}N(COOH)_{3}, and cinchomeronic acid, a pyridine-dicarboxylic acid, C_{5}H_{3}N(COOH)_{2}.  When distilled with potassium hydrate, quinine yields quinoline and its homologues.  The alkaloid has been shown to be a tertiary base.

Quinidine yields with chromic acid the same decomposition products as quinine.

Cinchonine, C_{19}H_{22}N_{2}O, the second most important alkaloid of these barks, when oxidized with potassium permanganate, yields cinchonic acid, which is a quinoline-carboxylic acid, C_{9}H_{6}N(COOH), cinchomeronic acid, which has just been stated to be a pyridine dicarboxylic acid, and a pyridine tricarboxylic acid.  When cinchonine is treated with potassium hydrate, it is decomposed into quinoline and a solid body, which on further treatment yields a liquid base, C_{7}H_{9}N, which is probably lutidine.  It has been found, moreover, that both tetrahydroquinoline and dihydroquinoline, hydrogen addition products of quinoline, are present.  When cinchonine is distilled with solid potassium hydrate, it yields pyrrol and bases of both the pyridine and quinoline series.

Cinchonidine, when heated with potassium hydrate, yields quinoline also, and with nitric acid the same products as cinchonine.

Strychnine has been found to be a tertiary amine.  When distilled with potassium hydrate, quinoline is formed.

Brucine is a tertiary diamine, that is, formed by substitution in a double ammonia molecule.  When distilled with potassium hydrate it yields quinoline, lutidine, and two isomeric collidines.